1. Field of the Invention
The present invention relates to a pinless folding apparatus for rotary printing presses, particularly for web-fed rotary printing presses.
2. State of the Art
U.S. Pat. No. 5,122,109 is related to a folding drum in a folding machine for a rotary press. In a known folding drum of a folding machine for use with a rotary press, a web to be cut on the folding drum is guided and held by a plurality of parallel bands aligned in the axial direction of the folding drum and spanning a gap of the folding drum. Tips of a folding blade project to the outside of the folding drum through the gaps between the respective bands. At least two bands are integrally connected by a respective band mount position with a plurality of groups of such integrally connected bands being provided. Each band mount position is mounted to the folding drum via respective adjusting devices such that the expansion of the bands of each group of the folding drum can be adjusted. Preferably, each adjusting device includes an adjusting plate engaged with an adjusting rack to which the bands are mounted and an adjusting shaft. The adjusting plate is mounted to the adjusting shaft at an eccentric position with respect to its engagement with the adjusting rack.
DE 295 02 957.9 is related to a folding cylinder having an adjustable diameter. The effective diameter of a folding drum can be adjusted on the run to handle products of different product thicknesses. By means of a spindle which is arranged in the center of a folding drum and which is in cooperative engagement with further spindles, closer to the circumference of the folding drum, belts on the circumference can be moved relative to the folding drum. A disadvantage of this device is that a lot of mechanical components are necessary to create a relative motion of the belts arranged on the outside of the folding drum.